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 A117618 Least number with complexity height of n, under integer complexity A005245. 3
 1, 6, 7, 10, 22, 683 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A005245 Complexity of n: number of 1's required to build n using + and * (and parentheses). A005520 Smallest number of complexity n: smallest number requiring n 1's to build using + and *. Now consider the recursion: A005245(n), A005245(A005245(n)), A005245(A005245(A005245(n))), ... which we know is finite before reaching a fixed point, as A005245(n) <= n. The number of steps needed to reach such a fixed point is the complexity height of n (with respect to the A005245 measure of complexity, there being others in the OEIS). REFERENCES W. A. Beyer, M. L. Stein and S. M. Ulam, The Notion of Complexity. Report LA-4822, Los Alamos Scientific Laboratory of the University of California, Los Alamos, NM, December 1971. R. K. Guy, Unsolved Problems in Number Theory, Sect. F26. LINKS W. A. Beyer, M. L. Stein and S. M. Ulam, The Notion of Complexity. Report LA-4822, Los Alamos Scientific Laboratory of the University of California, Los Alamos, NM, December 1971. [Annotated scanned copy] R. K. Guy, Some suspiciously simple sequences, Amer. Math. Monthly 93 (1986), 186-190; 94 (1987), 965; 96 (1989), 905. E. Pegg, Jr., Integer Complexity. Eric Weisstein's World of Mathematics, Integer Complexity. FORMULA a(n) = least k such that A005245^(n)(k) = A005245^(n-1)(k) but (if n>1) A005245^(n-1)(k) != A005245^(n-2)(k), where ^ denotes repeated application. EXAMPLE a(1) = 1 because the A005245 complexity of 1 is 1, already giving a fixed point. a(2) = 6 because it is the smallest x such that A005245(x) =/= x and A005245(x) = A005245(A005245(x)). a(3) = 7 because 7 is the least number x with complexity 6, thus taking a further step of recursion to reach a fixed point. a(4) = 10 because 10 is the least number with complexity 7. a(5) = 22 because 22 is the least number with complexity 10. a(6) = 683 because 683 is the least number with complexity 22. a(7) = the least number with complexity 683. CROSSREFS Cf. A003037, A003313, A005245, A005421, A005520, A025280, A061373, A064097, A076091, A076142. Sequence in context: A216348 A114949 A081359 * A015825 A243489 A164018 Adjacent sequences:  A117615 A117616 A117617 * A117619 A117620 A117621 KEYWORD nonn AUTHOR Jonathan Vos Post, Apr 07 2006 EXTENSIONS a(2)=6 inserted by Giovanni Resta, Jun 15 2016 STATUS approved

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Last modified December 15 22:02 EST 2019. Contains 330012 sequences. (Running on oeis4.)